Tire deflation pressure switch using a dimpling dome pressure

ABSTRACT

The tire deflation pressure switch will energize a means for indicating when the air pressure in the tire drops below a predetermined point. The pressure switch is based on a sealed enclosure comprising a thin shell dome shaped diaphragm forming one contact of the switch. The other contact provides a prestress force on the dome. When exposed to the pressure within the tire, the diaphragm will buckle if the pressure is greater than a preselected value. The buckle will appear as a small dimple in a portion of the dome. Means are provided to limit the dimpling of the dome.

United States Patent [191 Brubeck et al.

[ 1 TIRE DEFLATION PRESSURE SWITCH USING A DIMPLING DOME PRESSURE 75 1lnventors: William R. Brobeck; Buddy F. Lane,

both of Richmond. Ind.

[73 Assignee: Avco Corporation, Richmond. 1nd.

[22] Filed: Mar. 23, 1972 211 Appl.No.:2 37,386

[52] US. Cl. ZOO/61.25, 200/83 B, 200/83 N, 340/58 [51] Int. Cl. H01h35/24 [58] Field of Search ZOO/61.25, 83 B, 200/83 N, 83 P; 340/58;73/1465 [56] References Cited UNITED STATES PATENTS 3,675,198 7/1972Drown ZOO/61.25 3,423,552 1/1969 Sipin ZOO/83 B 2,103,214 12/1937 Coffin200/83 B [111' 3,743,801 July 3,1973

FOREIGN PATENTS OR APPLICATIONS 697,286 10/1965 Italy 73/1465 PrimaryExaminer-Robert K. Schaefer Assistant Examiner-Gerald P. Tolin Att0rneyCharles M. Hogan and Eugene C. Goodale [57] ABSTRACT The tire deflationpressure switch will energize a means for indicating when the airpressure in the tire drops below a predetermined point. The pressureswitch is based on a sealed enclosure comprising a thin shell domeshaped diaphragm forming one contact of the switch. The other contactprovides a prestress force on the dome. When exposed to the pressurewithin the tire, the diaphragm will buckle if the pressure is greaterthan a preselected value. The buckle will appear as a small dimple in aportion of the dome. Means are provided to limit the dimpling of thedome.

5 Claims, 3 Drawing Figures Patented July 3, 1973 3,743,801

REClEVER/INDICATOR TRANSMITTER I/II/IIIIIIIIIIIIII.

TIRE DEFLATION PRESSURE SWITCH USING A DIMPLING DOME PRESSURE BACKGROUNDThis invention relates to switches and more particularly to a pressureswitch for use in automobile tires to provide an indication that thetire has reached a dangerous degree of deflation.

Numerous prior patents have been granted on tire deflation devices.These devices have included mechanisms connected with the valve stem,mechanisms involving bellows, diaphragms, linkages, etc. These priordevices have included numerous moving parts which inherently decreasethe efficiency of such devices under operation. In addition, thedeflection obtained from bellows and numerous diaphragm configurationsis too gradual and not sufficient at low differential pressures toprovide adequate contact pressure and clearance.

Accordingly, it is an object of this invention to provide a tiredeflation pressure switch with no moving parts yet is efficient inoperation for providing switch- 7 ing effect in response to pressure.

Another object of this invention is to provide a device havingrepeatability of operation. A still further object of this invention isto provide a tire deflation pressure switch operate which can bedesigned to operate at any desired pressure.

SUMMARY This invention provides an improved tire deflation pressureswitch which can be mounted within the tire to the tire rims and wheels.The pressure switch comprises a thin shell spherical dome which is putunder mechanical stress. The dome cooperates with a second member todefine a sealed chamber, said chamber having a given fluid pressure. Thedome buckles in response to an pressure normally considerably greaterthan the pressure in the sealed chamber and returns to its dome shapewhen the excess external pressure is reduced.

Other objects, details, uses and advantages of this invention willbecome apparent as the following description of the exemplary embodimentthereof presented in the accompanying drawings proceeds.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings show apresent exemplary embodiment of this invention in which:

. FIG. 1 is a cross-sectional view of the pressure switch showing theswitch in the tire deflated position;

FIG. 2 is a view similar to FIG. 1 showing the switch in the pressurizedposition; and

FIG. 3 is a top view of the presuure switch of FIG. 1.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENT Reference is now made to thedrawings which illustrate one exemplary embodiment of the improved tiredeflation pressure switch of this invention, which is designatedgenerally by the reference numeral 10. The pressure switch is mounted tothe tire rim or hub (not shown) such that when a tubeless tire (notshown) is mounted on the rim the switch 10 is in communication with theinternal pressure of the tire. The switch 10 is comprised ofa thin shelldome shaped diaphragm 12. The diaphragm 12 is hermetically sealed byknown diaphragm 12 as one electrical contact, a terminal 18 beingsecured to the peripheral lip 20 of the diaphragm 12, and a bridge 22forming the other contact. A terminal 24 is secured to the bridge 22.The diaphragm l2 and shell 14 are electrically separated from the bridge22 by respectively mounting the parts on any suitable insulating pad 26.A contact 28 is secured to the bridge 22 so as to be in physical contactwith the dome diaphragm 12 under a given condition such as underinflation or deflation of the tire, as will be explained herebelow.

It is known that for the case of a spherical shell, if the stress of thematerial is held within its classic limits, the buckling wave isrestricted to a small dimple subtended by a solid angle of about 16. Inaddition, when a segment of a spherical shell is loaded by externalpressure, experiments have shown that only one single small buckleappears, whereas the rest of the shell remains in approximatelyspherical shape. These phenomena are respectively discussed in theJournal of Aeronautical Sciences, in articles appearing respectively inVol. 7, December 1939, No.2, pages 43-50, and August 1942, pages373-384.

Accordingly, the rigid shell 14 is so shaped within the dome diaphragm12 including a flat shape that the horizontal portion provides a limitor stop for the buckling or of the diaphragm 12 as seen in FIG. 2. Thelimiting of the deformation or buckling of the diaphragm 12 is locatedsuch that the angle of the small dimple is approximately l6 and wellwithin the elastic limit of the diaphragm 12 material. To insure thatthe dimple or buckling of the diaphragm 12 occurs in the correctlocation, the contact 28 provides a prestress force to the domediaphragm 12. The amount of prestressing of the diaphraghm 12 can bechanged by raising or lowering the bridge 22. This prestressing orpreloading may also be used as a convenient and efficient means toestablish the pressure at which the buckling takes place.

In operation, the pressure switch is installed to the hub or rim of thewheel within the tire and is thus exposed to the pressure within thetire. In the deflated condition the pressuresswitch remains in theposition shown in FIG. 1. As the tire is inflated, the switch 10 willremain in the position shown in FIG. 1 until the pressure within thetire excees the established pressure for buckling. At this point, thedome diaphragm 12 buckles and a small dimple is created on a portion ofthe dome diaphragm 12 as seen in FIG. 2. The dimple will appear in theplace where the dome diaphragm is preloaded with the contact 28 and theswitch is thereby placed in the open condition. When the pressure in thetire is reduced to below the buckling pressure, the elasticity of thematerial in the dome diaphragm 12 returns the diaphragm 12 to theunbuckled position wherein the diaphragm 12 makes contact with thecontact 28 thereby closing the switch. Means are provided for causingthe closing of the switch to display a visible or audible signal to theoperator of the vehicle to inform him that the tire is in need ofreinflation. As an example, the contacts 18 and 24 may be connected bylines 30 and 32 (FIG. 1) to any suitable electrical circuit such as atransmitter 34. The transmitter, when acti-- vated by the closing of theswitch 10, transmits a signal to any suitable receiver/indicator 36. Itis obvious that numerous configurations of transmitter and receiver[indicators may be utilized in conjunction with the switch of thisinvention and the diagrammatic representation of FIG. 1 is only forexplanatory purposes. When the tire is reinflated, the dome diaphragm 12will once again buckle and open the switch 10. By holding thedeformation of the dome diaphragm 12 to a small dimpie or buckling, theelastic limit is not exceeded, thereby assuring repeatability of thebuckling or dimpling effect.

The material thickness of the dome diaphragm 12 may also be used tocontrol the operational pressure at which buckling will occur. As anexample, if the thickness of the dome diaphragm is increased, it willrequire a greater tire pressure to cause the buckling.

It can be seen that the pressure switch hereinabove described has nomoving parts, yet is efficient in operation for providing an on-offswitching effect in response to pressure. Accordingly, the objectiveshrereinbefore set forth have been accomplished.

While a present exemplary embodiment of this invention has beenillustrated and described, it will be recognized that this invention maybe otherwise variously embodied and practiced by those skilled in theart.

What is claimed is:

l. A pressure switch for mounting within an external pressure chamberfor monitoring the pressure within the pressure chamber, the pressreswitch comprising:

a thin shell dome diaphragm forming one contact of the switch;

a rigid shell, said diaphragm and shell being sealed together to definea permanently sealed fluid filled chamber therebetween;

a second contact secured in fixed relationship to said dome diaphragmand being engageable with said diaphragm to assert a prestress forcethereon, said second contact engaging said diaphragm when externalpressure surrounding the switch is less than a predetermined pressure;

said dome diaphragm being responsive to the external pressuresurrounding the switch wherein said diaphragm buckles away from thepoint of prestress force to form a dimple in a portion of said domediaphragm when the external pressure exceeds a predetermined pressurethereby providing an open switch condition, said dome diaphragmreturning to the unbuckled position to provide a closed switch positionwhen the external pressure surrounding the switch becomes less than thepredetermined pressure;

means for electrically insulating said second contact from said domediaphragm; and

means connected with said diaphragm and second contact to provide anindication of the external pressure condition surrounding the switch.

2. The pressure switch as set forth in claim 1 in which said secondcontact comprises a bridge member mounted over said dome diaphragm acontact being secured to said bridge and being engageable with said domediaphragm in the location where the dimpling deformation is desired.

3. The pressure switch as set forth in claim 1 in which said insulationmeans is an insulating pad on which said second contact means and domediaphragm are mounted to provide the fixed relationships 4. The pressureswitch as set forth in claim 1 in which said rigid shell is formed witha horizontal portion, said horizontal portion providing a buckling limitwhereby the dimpling deformation of the dome diaphragm is limited bysaid horizontal portion of said rigid shell.

5. The pressure switch as set forth in claim 4 in which said horizontalportion which limits-the dimpling deformation is located within saiddome diaphragm.

UNITED STATES PATENT OF FICE CERTIFICATE OF CORRECTION Patent No.3,743,801 Dated July 3, 1973 Inventor(s) William R. Brobeck and Buddy F.Lane It is certified that error appears in the above-identified patent.and that said Letters Patent are hereby corrected as shown below:

In column 3, claim 1, line 37, the word insulatedly"- should appearbefore "secured"; line 38,

' the words "dome diaphragm" should be changed to rigid shellv column 4(claim 1) line 14 "and" should appear after the semicolon; and lines 15and 16 in column 4 should be cancelled;

Column 4, claim 3 lines 26 29 should read 3. The pressure switch as setforth in claim 1 further comprising an insulating pad, said secondcontact and dome diaphragm being mounted thereon to provide the fixedrelationship.

Signed '.and sealed this 2nd day of July 1974.

(SEAL) .Attest:

EDWARD M. FLETCHERJR. c. MARSHAL-L DANN Attesting Officer Commissionerof Patents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PatentNo. 3,743,801 Dated July 3, 1973 Inventor(s) William R. Brobeck andBuddy F. Lane It is certified that error appears in the above-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

In column 3, claim 1, line 37, the word insulatedly should appear before"secured"; line 38 the words "dome diaphragm" should be changed to rigidshell column 4 (claim 1) line 14, "and" should appear after thesemicolon; and lines 15 and 16 in column 4 should be cancelled;

Column 4, claim 3, lines 26 29 should read 3. The pressure switch as setforth in claim 1 further comprising an insulating p'ad, said secondcontact and dome diaphragm being mounted thereon to provide the fixedrelationship.

Signed'and sealed this 2nd day of July 1974.

(SEAL) .Attest:

EDWARD M.FLETHER,JR. c. MARSHALL DANN Attestlng Officer Commissioner ofPatents

1. A pressure switch for mounting within an external pressure chamber for monitoring the pressure within the pressure chamber, the pressre switch comprising: a thin shell dome diaphragm forming one contact of the switch; a rigid shell, said diaphragm and shell being sealed together to define a permanently sealed fluid filled chamber therebetween; a second contact secured in fixed relationship to said dome diaphragm and being engageable with said diaphragm to assert a prestress force thereon, said second contact engaging said diaphragm when external pressure surrounding the switch is less than a predetermined pressure; said dome diaphragm being responsive to the external pressure surrounding the switch wherein said diaphragm buckles away from the point of prestress force to form a dimple in a portion of said dome diaphragm when the external pressure exceeds a predetermined pressure thereby providing an open switch condition, said dome diaphragm returning to the unbuckled position to provide a closed switch position when the external pressure surrounding the switch becomes less than the predetermined pressure; means for electrically insulating said second contact from said dome diaphragm; and means connected with said diaphragm and second contact to provide an indication of the external pressure condition surrounding the switch.
 2. The pressure switch as set forth in claim 1 in which said second contact comprises a bridge member mounted over said dome diaphragm a contact being secured to said bridge and being engageable with said dome diaphragm in the location where the dimpling deformation is desired.
 3. The pressure switch as set forth in claim 1 in which said insulation means is an insulating pad on which said second contact means and dome diaphragm are mounted to provide the fixed relationship.
 4. The pressure switch as set forth in claim 1 in which said rigid shell is formed with a horizontal portion, said horizontal portion providing a buckling limit whereby the dimpling deformation of the dome diaphragm is limited by said horizontal portion of said rigid shell.
 5. The pressure switch as set forth in claim 4 in which said horizontal portion which limits the dimpling deformation is located within said dome diaphragm. 